The present invention relates to photopolymerizable compositions and to photosensitive plates developable with water, said plates being directly utilizable as printing plates per se and also being useful for the production of relief images. More specifically, the present invention relates to a novel photosensitive plate which may be developed without the need for any pre-exposure conditioning and which provides a printing plate having improved printing characteristics.
Several photopolymerizable elements which are useful as printing plates have been disclosed in the prior art. One such disclosure is that of U.S. Pat. No. 3,801,328 issued to Takimoto et al. While the photopolymerizable compositions and elements disclosed in the Takimoto et al patent have met with considerable success, they nevertheless suffer from the disadvantage which is typical of prior art compositions and elements, that in order to produce a satisfactory relief image in such an element, it is necessary to subject the element to a pre-exposure conditioning. More specificially, the prior art teaches that when using photopolymer compositions of the type used in the present invention, it is necessary to reduce the presence of oxygen in the photopolymer in order to obviate the polymerization inhibition which oxygen effects during the exposure of the photopolymer to actinic light. The prior art teaches that such oxygen reduction or removal may be effected by CO.sub.2 conditioning or by a brief light exposure or "bump exposure" immediately prior to the imagewise exposure of the photosensitive element. Of course, such preconditioning of the photosensitive elements results in greater processing costs and increased processing time and energy consumption.